The development of sensitive, specific and universal assay is needed to determine the role of apoptosis in biology and in tumor cell response to chemotherapy. A novel anti-ssDNA MAb assay developed by the applicant is designed to meet these requirements. The assay is based on the staining of apoptotic cells with a new monoclonal antibody (MAb) highly specific for single-stranded DNA. Importantly, MAb assay detects apoptosis in tissue sections, for which the only other available histochemical marker (TUNEL) has low sensitivity and limited specificity. The major goal of this proposal is validation of a novel anti-ssDNA MAb apoptosis assay against other available tests: annexin V staining, activation of caspases, decrease in mitochondria membrane potential and DNA fragmentation (TUNEL staining and DNA ladder). Modified protocols, which make possible application of the technique to archival and biopsy material, will be developed. The assay will be tested in different models in order to prove universal application and to determine correlation with drug sensitivity: apoptosis induced by cytotoxic agents, hormones, ligation of FAS receptor, apoptosis in hematopoetic and epithelial cell lines and apoptosis in drug-sensitive and drug resistant cell lines and solid tumors. PROPOSED COMMERCIAL APPLICATION: To market apoptosis assay.